The invention relates to a method for the guidance of aircraft on taxiways.
NLA (New Large Aircraft, e.g. Airbus A3XX) feature larger dimensions than the largest commercial aircraft, Boeing B 747, today. ICAO (International Civil Aviation Organization), ACI (Airports Council International) and aircraft manufacturers therefore are looking for solutions on how NLA can land, taxi and be dispatched on existing airports without the need for costly new constructions or modifications.
The A3XX could safely maneuver on taxiways (taxiways code E/group V) certified for the B 747, including turns and branch-offs, when the main landing gear""s lateral deviation from the taxiway centerline is a maximum of 0.5 m. Turns, among other things, require considerable oversteering of the nose landing gear or steering of the nose landing gear along an invisible aircraft-specific ideal line which considerably deviates from the centerline.
A pilot is not able to achieve the required lateral precision and the taxiing along an ideal line, to be calculated for the nose landing gear, via manual control.
Navigation systems are known for road vehicles featuring the following components, among other things:
Inertial system (autonomous navigation systems based on motion sensors, e.g. wheel rotation measurement and electronic compass) with errors which, in general, are proportionate to either the distance covered since the last waypoint or to the time passed (gyro systems)
Satellite navigation system, as necessary (on account of masking and interfering multipath signal reception from various satellites; such a system can be used in road traffic only for accuracies in the range of approx. 100 m); as a rule only to support an inertial system
Digital road map including storage of the course of all roads and turn-off possibilities of the road network
Map matching method to continuously compare the path pursued by the inertial system with the stored road network and utilization of every tight turn and every turning-off as a waypoint for the inertial system.
An accuracy of approx. 5 m can be achieved with this combination (possibly also without satellite navigation), which is sufficient for guidance to destination (e.g. voice output to the driver xe2x80x9cturn right after 50 mxe2x80x9d).
The object of the invention is to provide a method for the guidance of aircraft on taxiways by means of which aircraft can be guided with a lateral deviation of less than 0.5 m from the ideal line. New large aircraft, in particular, are to taxi safely on existing taxiways.
The task is achieved by means of the method according to claim 1. Advantageous designs are the subject of subclaims.
According to the invention, it is proposed to transfer the method known for the navigation of road vehicles to the guidance of aircraft on taxiways. To this effect, individual lights of the taxiway lighting (preferably the lights of the centerline lighting) are used as navigation waypoints. The system to carry out the method according to the invention, includes the following components:
aircraft-typical inertial system, e.g. an inertial navigation system. An additional, aircraft-independent navigation system, such as a satellite navigation system, however, may be used too. It is also possible to use several navigation systems in parallel. The navigation system must provide only a limited accuracy (typically 10 m), which by itself is not sufficient to solve the basic task of the invention.
storage medium with reference information, especially in the form of a digital taxiway map. It contains the precise coordinates of the rim apertures of all lights of the planned taxiways and aprons which are suitable as waypoints. The precision of the coordinates contained in the taxiway map, for instance is approx. 10 cm.
additional sensor for the detection of lights and their position measurement. The latter should be performed with a precision of approx. 10 cm. Video cameras and scanners, for example which can be advantageously arranged on the aircraft main landing gear, are suited for this task.
map-matching method for the continuous comparison of the path pursued by the inertial system with the stored taxiway network and utilization of every detected light as a waypoint for the inertial system.
Using this combination, accuracies in the aircraft position determination of markedly better than 0.5 m can be achieved, allowing an automatic lateral guidance and the correct performance of the nose landing gear oversteering.
The taxiway to be used can be chosen by pilot input (as agreed with the tower) or by data transmission from the tower. Light detection by the sensor can be facilitated in that only the lights on the planned taxiway are switched on.
The method according to the invention is not limited to NLA but can be used for all aircraft and vehicles moving on areas fitted with lights. The degree of automation may differ widely and feature the following forms:
manual taxiing by the pilot with the help of guidance information generated by the system, e.g. voice output, visible overlays in the head-up display or on a monitor,
semi-automatic taxiing with automatic steering and manual longitudinal guidance (accelerating, braking) by the pilot,
automatic taxiing, including monitoring by the pilot, as necessary.